Market demand for biorenewable polymers is expected to increase by about 18% annually through the year 2018 with non-biodegradable bioplastics growing from around 8% to about 47% of the bioplastic market over the same period due to a range of applications for renewably based polymers and consumer desire for increased sustainability and energy independence.
Polyamides (PA), also known as Nylons, are an important class of engineering thermoplastics with a variety of applications. With the exception of PA-11, polyamides are typically derived from non-renewable fossil resources. However, the source of the polyamides is changing as more monomers become available from renewable resources. Blends of different types of Nylons are an established art, for example blends of aliphatic and aromatic polyamides find application in the automobile industry. Generally, the scientific and patent literatures suggest that aromatic-aliphatic blends are thermodynamically miscible but that aliphatic-aliphatic blends are usually immiscible.
Polymer blends are an established science but a number of rather fundamental issues remain. Polymers typically form immiscible blends. The large molecular weight of polymers limits the entropic contribution to free energy of mixing so that relatively small unfavorable enthalpy of mixing values lead to phase separation. Therefore, a large portion of polymer blending research is conducted on immiscible polymer systems—including the effects of compatibilization agents and blending techniques on the properties and morphology of immiscible blends.
Two examples of aliphatic polymers include PA-11 and PA-610. Desirable properties of PA-11 include high impact and abrasion resistance, low specific gravity (density of 1.03 g/cm3), excellent chemical resistance, low water absorption, and high thermal stability (melting point between about 180-190° C.). Applications for PA-11 include oil and gas pipelines, hydraulic and pneumatic hoses, powder coatings, skis, snowboards and optical fiber sheathing.
PA-610 is also a high-performance, semi-crystalline polymer. Important properties of PA-610 include low water uptake, hydrolysis resistance, stress cracking resistance, resistance to fuels, oils, greases, most solvents, aqueous solutions and alkalis. PA-610 has excellent flexural stiffness, dimensional stability, heat deflection temperature and high thermal stability (a melting point near 220° C.).
A recent review on all known miscible crystalline/crystalline polymer blends was published by Liu, J. P.; Jungnickel, B. J. Journal of Polymer Science Part B-Polymer Physics, 2007, 45, (15), 1917-1931. This review discusses the few known miscible crystalline/crystalline polymer blends and notes the strange kinetic and structural phenomena. Crystallization induced phase separation has been treated theoretically based on derivatives of a theory originally proposed by Dorgan (Dorgan, J. R. Journal of Chemical Physics, 1993, 98, (11), 9094-9106 and Dorgan, J. R.; Yan, D. Macromolecules 1998, 31, (1), 193-200) for simultaneous phase separation and ordering in liquid crystalline polymer blends.
Other PA blend literature consists mainly of polyamide-6 or polyamide-6,6 blended with various additive polymers including styrene, polypropylene, ABS, or with rubber toughening additives. There are several papers considering aliphatic PAs blended with aromatic PAs, but limited number of publications on aliphatic only PA blends. It has been shown that miscible aliphatic nylon blends, are rare, but do exist. Some of these miscible blends are polyamide 4,8/polyamide 6,6 and polyamide 6,6/polyamide 6. There are some sources on the interchange reactions that occur between the polyamide end groups to form block co-polymer in-situ. The blending time required to form significant interchange reactions is upwards of 3 hours at temperatures of 300° C.
There is a need for a miscible polymer blend that can be used in a large variety of applications that are manufactured at low temperature and short durations.